Mediterranean Basin

Description

Uniquely located at the crossroads of Europe, Asia and Africa, the Mediterranean Basin is one of the most biologically rich and complex regions on Earth (1). With almost 12,000 of its species found nowhere else, the Mediterranean Basin is considered to be one of the planet’s biodiversity ‘hotspots’, due to the region’s high level of endemism(2).

Having been occupied by humans for around eight thousand years, the Mediterranean Basin has unsurprisingly undergone dramatic alterations from the original major vegetation type of oak, deciduous and conifer forests...

Mediterranean Basin fact file

Description

Uniquely located at the crossroads of Europe, Asia and Africa, the Mediterranean Basin is one of the most biologically rich and complex regions on Earth (1). With almost 12,000 of its species found nowhere else, the Mediterranean Basin is considered to be one of the planet’s biodiversity ‘hotspots’, due to the region’s high level of endemism(2).

Having been occupied by humans for around eight thousand years, the Mediterranean Basin has unsurprisingly undergone dramatic alterations from the original major vegetation type of oak, deciduous and conifer forests (2). Despite this, the region is still home to a dramatic variety of habitats, including pine forests, mountain ranges up to 4,500 metres high, floristically spectacular scrublands and stretches of dramatic coastline (2)(3). It also boasts the world’s largest inland sea, the Mediterranean Sea, which covers 2.5 million square kilometres and is home to a remarkably diverse selection of marine life (1)(3)(4).

The Mediterranean Basin has what is termed a ‘Mediterranean climate’, which describes the distinct, subtropical climate shared by five regions around the world, of which the Mediterranean Basin is the largest (5). This climate is typified by hot, dry summers and cool, wet winters (5). In spite of this generalisation, the temperature and rainfall can vary greatly throughout the region, with the mean annual rainfall ranging from as little as 100 millimetres in some areas to over 4,000 millimetres in others (1). The climate is also generally considered to be harsher on the northern than the southern shores of the Mediterranean Sea (1).

Range

The Mediterranean Basin encompasses the area surrounding the Mediterranean Sea, and covers 2,085,292 square kilometres (2). It includes 24 countries which are spread across 3 continents.

From west to east the Mediterranean Basin stretches around 3,800 kilometres between Portugal and Lebanon, and around 1,000 kilometres north to south, from Italy to Morocco and Libya (1)(3). It also includes some 5,000 islands around the Mediterranean Sea and the Macaronesian islands in the North Atlantic Ocean (2).

Biodiversity

Plants

The Mediterranean Basin is particularly noted for its spectacular array of endemic plants, with 52 percent of the 22,500 species found nowhere else in the world (2). The level of endemism is especially high on the islands of the Mediterranean, where species have evolved to survive in very specific habitats (2)(6). The Maltese rock-centaury (Cheirolophus crassifolius) grows only on the windy cliffs of Malta (3) whilst the pink-flowered Silene hicesiae is only known to occur on the slopes of two volcanic islets (7).

Due to the long history of human occupation in the Mediterranean Basin, many of the forests have been replaced by floristically rich scrubland (2). This ubiquitous Mediterranean scrub is sometimes classified in to different types, depending on factors such as the plant composition and soil type, although the boundaries between these are blurred, producing a mosaic of plant communities (3)(8). Perhaps the most iconic inhabitant of the scrubland is the olive tree (Olea europaea), a small, evergreen tree best known for its edible fruit (3)(9). A range of familiar aromatic shrubs such as lavender (Lavandula), thyme (Thymus) and rosemary (Rosmarinus) also grow there, along with medically important plants like felty germander (Teucrium polium)(3)(10). As well as providing an array of habitats, this complex mixture of plants puts on a spectacular floral display every spring (3).

The forested areas of the Mediterranean Basin are much more diverse than those found in other areas of Europe (2)(3). Of the 290 tree species native to the Mediterranean Basin, an incredible 201 are endemic(2). The cedar of Lebanon (Cedrus libani) in particular is renowned for its timber, having been utilised for thousands of years and now holding pride of place on the Lebanese flag (11). The only palm species native to Europe, the Cretan date palm (Phoenix theophrasti), is also found in the Mediterranean Basin, existing in a few scattered populations in Crete and Turkey (12)(13).

The Mediterranean Sea is host to a range of unique plants, including up to 200 endemic macroscopic species (4). One of the most important marine vegetation types, however, is the meadows of seagrass, such as Posidonia oceanica, which supports over 80 percent of the fish yield in the Mediterranean (4).

Mammals

Despite the Mediterranean Basin having fewer mammal and bird species than other biodiversity ‘hotspots’, it is still home to 220 mammal species, an impressive 11 percent of which are endemic to the region (2).

As well as being home to around 500 species of bird, 25 of which are endemic, the Mediterranean Basin is an important migration route, with some two billion birds travelling to, or through, the region every year (2)(3).

Encompassing both freshwater and marine habitats, the Mediterranean Basin unsurprisingly has a wide range of aquatic inhabitants. The Mediterranean Sea is home to some 519 species of bony fish, sharks and rays, of which 74 species are endemic(14). The freshwater habitats are also very diverse, with 60 endemic species, including the Ghizáni (Ladigesocypris ghigii), which has recently been saved from extinction by careful management of its habitat (2)(14).

With so many plants in the Mediterranean region there is an associated high diversity of invertebrates(3). About 75 percent of the estimated 150,000 European invertebrate species occur in the Mediterranean Basin (16). Scorpions, cicadas, dragonflies and a array of colourful butterflies are but a few of the invertebrate groups that live there (6).

Threats

Having been occupied by humans for some 8,000 years, the Mediterranean Basin has been under human influence for far longer than any other biological ‘hotspot’ (2). Currently home to around 455 million people, the Mediterranean region is also visited by an additional 246 million tourists every year (14). The pressure from this volume of people is causing severe degradation of the Mediterranean’s natural environment, and only five percent of the original habitat remains unaltered (2)(14).

For centuries, the farming systems of the Mediteranean Basin have existed as a delicate balance between productivity and wildlife conservation (7). However, ancient practices have been abandoned in recent years in favour of intensive, industrial-scale methods (3)(7). Deforestation, intensive grazing and fires have all led to the loss of habitat vital to endemic species (2). Development for the tourism industry has also placed a great deal of pressure on coastal habitats, with the construction of hotels and holiday homes resulting in many areas of coastline disappearing under concrete (2)(3).

Freshwater ecosystems are under particularly high pressure, with the demand for water for crop irrigation approaching unsustainable levels (3)(14). There are also more than 3,500 dams in Mediterranean rivers, permanently altering the flow regime and habitat of many species (14). As a result, more than 56 percent of endemic freshwater fish are currently classified as being threatened with extinction (14). Pollution, invasive species and climate change are all also impacting on the biodiversity of the region (14).

Conservation

Conservation in the Mediterranean Basin is by no means a new concept, with areas of natural resources being set aside by the Greeks and Romans for protection up to 2,000 years ago (2). However, today as little as 4.3 percent of the Mediterranean Basin is set aside as protected areas. A major conservation aim is to expand these protected areas, although there are fears these will still be too small to support populations of threatened endemic species (2).

A conservation method that has met with some success is the creation of biosphere reserves, where the resources and land within the reserve are allowed to be used in a sustainable manner. This strategy of balancing conservation with the needs of people is likely to be important in the success of any conservation measure in the Mediterranean (2). A number of other management plans have also been implemented, including the Strategic Action Programme for the Conservation of Biological Diversity (SAP BIO), which aims to assess the marine and coastal biodiversity of the Mediterranean Basin and identify the best ways to enhance and protect these important habitats (17). There is also currently a 25 year plan to reduce land-based pollution (4).

Despite still facing many pressures, the Mediterranean Basin’s recognition as a global biodiversity ‘hotspot’ provides hope for its future, with these hotspot areas being recommended as conservation priorities (18).

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